PM should be activated for a number of reasons. For instance, it allows the continuance of dialog between two individuals that initiates in a given thread but subsequently refocuses to technical areas of mutual scientific interest that are now inconsistent with the original intent (topic) of that thread.
PM also enables information mentoring, for want of a better term. For instance, one member may wish to learn from the knowledge base and expertise possessed by another by asking very specific yet perhaps basic questions relating to his or her technical area. This hesitation may simply be a matter of pride or vanity or it may relate to some other issue of practical concern such as expectations held by others (exaggerated or not) about the overall technical competency of that member by virtue of title or standing in the general scientific or corporate community. PM overcomes this hesitation and promotes learning in this regard because of its private nature.
In general the greater the opportunity for interaction, the better. This is after all, the Information Age
, is it not? IMHO...for these and other goodly reasons I submit that Private Messaging is a value added service and should be turned on. Thank you for your consideration, LL